In fiction, while some characters are ‘two-dimensional’, others seem to have real ‘depth’. They can, indeed, assume in our imagination, a vividness that may equal, or even exceed, that of some of our living acquaintances. We may attribute them with attitudes and beliefs that go far beyond the printed page. Yet such apparent depth is, of course, an illusion: there are no facts about Anna Karenina’s life, save what Tolstoy gives us; no hidden motives lurking between the lines.

The shocking truth is that the behaviour of real people is no different. There are the facts of what people say and what they do; and these, like the lines of a novel, can conjure up a compelling depth – of underlying motivations, beliefs and attitudes from which people’s behaviour appears to emerge. However, as for fictional characters, so with real people: the sense that behaviour is merely the surface of a vast sea, immeasurably deep and teeming with inner motives, beliefs and desires whose power we can barely sense is a conjuring trick played by our own minds. The truth is not that the depths are empty, or even shallow; but that the surface is all there is.